Whirring noise - soft whoowhoo sound 1999 Honda Accord

My 1999 Honda Accord is making a whirring noise sometimes. It happens occasionally, now more frequently than last month. It sometimes happens when I start the engine, but am still in Park. Mostly it happens when I’m actually driving. both slowly on back roads and fast on the highway. What would cause this?

If it happens when the car is not moving, then it is most likely the serpentine belts or related pulleys and bearings.

Thanks. I’m bringing the car to my mechanic on Monday. I don’t want to have to pay for unnecessary stuff, if we can get right to the cause.